Recently, there have been many improvements in stroller design. Lighter weight of the whole structure of the stroller, safety during using it, and small volume of it after collapsing have all become focuses to be improved, and the emphasized points that are particularly put on are the material of the frames, collapsing structure, safety fastener, braking structure, and damping design etc. of the stroller. Due to the above improvements, the weight is lighter, the volume is smaller, safety is enhanced, and comfort is significantly upgraded in the present stroller. However, such improvements inevitably and largely increase the cost of manufacturing a stroller and add cost to consumers.
Importantly, there is seldom improvement about the wheel device per se in the prior art. However, the wheel device plays a vital role in the stroller operation because the stroller must be apt to move on different roads. Even if the road is uneven, the wheels are by no means allowed to be separated from the stroller. Besides, the smoothly rolling of the wheels must be taken into consideration at the same time, that is, the fixation of the wheels should not affect their smoothly rolling.